Turbocharger Failure Analysis - by Gus Wright

Turbocharger Failure AnalysisGus Wright

Symptoms of Turbo Failure1. Low or no boost (Performance complaints)2. Noise3. Oil leakage4. Poor transient response (i.e Lazy – lag)5. Blue smoke6. Fault codes7. Excessive combustion temperature (i.e. Heatdamaged cylinder components, exhaust manifoldand exhaust pipes)Causes of turbocharger failure – varied

Verifying Performance Complaints• Must road test or use dynamometer toverify low power complaint.• Intake boost pressure which meetsminimum specifications generally meansthe turbocharger and engine areperforming satisfactory.

Low Boost = Low-powerBoost pressure gaugeNo/low fuel = no boost.Restricted air flow =poor combustion andlow-boost

Sources of NoiseBearings & Leaks

NoiseSome turbochargers willcreate unusual noisesduring acceleration.“Warble” or (Woofing orbarking duringdeceleration)” iscommonly caused bysurge – when thecompressor wheel speedis unable to correctlymove air due toaerodynamics of thehousing.

Bearings – CokedCoked bearings caused by hot shut-down.Causes contact of rotating compressor or turbine wheel with turbohousings

Bearings• Bearing damage due to hot shut down

Pre-lube Turbo Bearings!

Inspecting Turbo BearingsUp & Down –radial play.In & Out – Axialplay

Bearing Inspection• One technique formeasuring radialmovement

Axial End-Play Measure

Turbine Shaft DamageHot shut-down

Compressor Wheel Damage• Note differencebetween damagecaused by hardand soft objects

Compressor Wheel Damage

Oil leakage• Oil leakage isnot acceptable.• Too much idling,• High crankcaseblow-bypressure• Worn/damagedseals

Oil leakage 1• All turbos wisp someoil.• Crankcase oil isdrawn intoturbochargers ofsome closedcrankcase systems.Intercooler hoses weeping oil

Evaluating Oil Leaks

Turbine Seal DamageMissing oil seal

Turbine Oil Seal